I am hooking up an aftermarket alarm. I disconnected the factory alarm, and the car will not start. I hook it back up, it starts. Do you have to leave the factory alarm connected when installing an aftermarket alarm? Thanks for any help.

 

I believe you do have to keep the factory one hooked up because when you unplug it the starter kill kicks in. I still have my factory one hooked up I just disconnected the siren from the factory alarm

 

I have both alarms working. The aftermarket alarm control my existing one. Actually all you need is to connect one wire from aftermarket alart (pulse before start if it's remote starter) to disarm wire on security module under passenger seat.